1. Field of the Invention
The present invention relates to a data processing apparatus for, e.g., a laser printer or the like, which receives image data from an external apparatus and prints a recording image on a paper sheet in accordance with the received data.
2. Description of the Related Art
Conventionally, image formation of a data processing apparatus for, e.g., a laser printer or the like, is performed by the steps of charging, exposure, development, transfer, separation, cleaning, fixing, and the like. In a data processing apparatus of this type, a charger, an exposure unit, a developing unit, a transfer unit, a separation unit, a cleaning unit, and the like are sequentially arranged around a photosensitive drum. A fixing unit is also provided for receiving a paper sheet from the separation unit. These units are driven in accordance with the rotational movement of the photosensitive drum to execute the respective image forming steps, thereby forming an image on a paper sheet.
In a laser printer of this type, two separate control systems are provided for an engine control circuit for controlling the respective units to execute the respective image forming steps, and a printer control circuit for controlling the operation of the engine control circuit. The engine control circuit and the printer control circuit are interfaced by exchange of commands and status signals. The printer control circuit receives image data in units of pages, which is supplied from an external apparatus, forms by developing bit image data (bit map data) from the image data, and outputs the bit image data to the engine control circuit.
In the laser printer of this type, an IC card or a memory cartridge which has a memory unit storing character patterns is mounted. The image data in units of pages which is supplied from an external apparatus is developed to bit image data (bit map data) by using the character patterns stored in the IC card or the memory cartridge.
When a large number of character types are to be printed, however, an IC card or a memory cartridge that stores a large number of character types must be prepared, or, a data processing function such as a deriving function must be incorporated in the laser printer.
As a result, when a large number of character types are to be printed, a memory unit having a large memory capacity is required for an IC card or a memory cartridge, or the printing speed is decreased due to the data processing function.